A. Field of Invention
The present invention is in the fields of polymers and electronics, including organic electronics, plastic electronics, and organic semiconductor devices. In particular, it concerns a crosslinker, and a method of making a device using a crosslinker.
B. Background Information
Radiation- or thermal-induced crosslinking of insulating, semiconductive and conductive polymer films is a crucial enabling step in the fabrication of multilayered device components and integrated circuits (ICs). This allows for the repeated deposition or patterning of multilevels in the device and/or the IC. One way to achieve radiation crosslinking is through the use of radiation-sensitive crosslinkers. Although such materials have been commercially available for a long time, most of them are not generally applicable to organic polymer semiconductor device technologies because of the severe restrictions on purity. The crosslinking has to be performed without causing degradation of the electrical performance of the device. This often requires the stringent exclusion of electrical traps, from the crosslinked products or by-products, and for applications in light-emitting diodes, also of states that could interact with and degrade the luminescence efficiency of the semiconductive material. A number of radiation crosslinking systems have been recently disclosed using oxetane reactions, epoxy reactions, cinnamate dimerisation reactions.
The crosslinking of water-soluble conductive polymer systems using bis(phenyl azide) crosslinkers have been proposed for the interconnects and electrodes in organic semiconductor device technologies [F. J. Touwslager, N. P. Willard and D. M. de Leeuw, “I-line lithography of poly(3,4-ethylenedioxythiophene) electrodes and application in all-polymer integrated circuits”, Applied Physics Letters, 81 (2002) pp. 4556-4558]. In the cited literature, a high concentration of the crosslinker is required, typically in excess of 10 w/w %. This suggests that the crosslinking efficiency is relatively low, and there is a high concentration of by-products generated. This is probably suitable for a range of applications that are not sensitive to these by-products.
In view of the above, there is a need to obtain improved crosslinkers, preferably with high efficiency and minimum concentration of by-products generated. Further, it is a preferable aim of the present invention to provide single and/or multilayer structures in organic electronic devices obtained from the crosslinkers. Another preferably aim of the present invention is to provide a new method for making the devices.